Access node for end-to-end beamforming communications system
Methods and systems are described for providing end-to-end beamforming. For example, end-to-end beamforming systems include end-to-end relays and ground networks to provide communications to user terminals located in user beam coverage areas. The ground segment can include geographically distributed access nodes and a central processing system. Return uplink signals, transmitted from the user terminals, have multipath induced by a plurality of receive/transmit signal paths in the end to end relay and are relayed to the ground network. The ground network, using beamformers, recovers user data streams transmitted by the user terminals from return downlink signals. The ground network, using beamformers generates forward uplink signals from appropriately weighted combinations of user data streams that, after relay by the end-end-end relay, produce forward downlink signals that combine to form user beams.
1. An access node for communication in a communication system comprising a plurality of access nodes at geographically distributed locations providing a communication service to user terminals distributed over multiple return user beam coverage areas via an end-to-end relay comprising multiple return receive/transmit signal paths, comprising:
means for receiving a return downlink signal from the end-to-end relay, the return downlink signal comprising a relay beacon signal and return uplink signals from a plurality of the user terminals relayed by the end-to-end relay, to form a composite return signal;
means for obtaining receive timing information based on the relay beacon signal;
means for multiplexing the composite return signal with the receive timing information to obtain a multiplexed composite return signal; and
means for sending the multiplexed composite return signal to a return beamformer.
2. The access node of claim 1 , wherein the means for obtaining determines a receive timing adjustment and a receive phase adjustment to compensate for downlink channel impairment based at least in part on a comparison of the relay beacon signal to a local reference signal.
3. The access node of claim 2 , further comprising: means for adjusting timing of the composite return signal based on the receive timing adjustment.
4. The access node of claim 2 , further comprising: means for adjusting a phase of the composite return signal based on the receive phase adjustment.
5. The access node of claim 1 , wherein the multiplexed composite return signal comprises a plurality of time-domain subsets of samples.
6. The access node of claim 5 , further comprising means for interleaving samples of the multiplexed composite return signal in the plurality of time-domain subsets of samples.
7. The access node of claim 1 , wherein the relay beacon signal comprises a pseudo-noise (PN) code.
8. The access node of claim 1 , wherein the relay beacon signal comprises frame timing information.
9. The access node of claim 1 , wherein the relay beacon signal comprises a plurality of signals at a plurality of sub-bands.
10. The access node of claim 1 , wherein the composite return signal comprises a circularly polarized signal and the relay beacon signal comprises a linearly polarized signal.
11. The access node of claim 1 , wherein the communication system has a first number of the access nodes and the end-to-end relay has a second number of the return receive/transmit signal paths, wherein the first number is different than the second number.
12. The access node of claim 11 , wherein the first number is greater than the second number.
13. The access node of claim 1 , wherein the end-to-end relay is a satellite.
14. The access node of claim 1 , wherein the composite return signal comprises a plurality of signals in different frequency sub-bands.
15. The access node of claim 14 , wherein the multiple return user beam coverage areas comprise a plurality of subsets of return user beam coverage areas associated with the different frequency sub-bands.
16. The access node of claim 15 , wherein each of the plurality of subsets of return user beam coverage areas comprises a plurality of non-overlapping return user beam coverage areas.
17. The access node of claim 14 , wherein a bandwidth for each of the different frequency sub-bands is greater than or equal to 500 MegaHertz.